Interface system isolating a subscriber subset from a telephone switching system

ABSTRACT

An interface system for installation in a centralized location remote from the customer&#39;s premises. A single line is employed in normal operation between the customer&#39;s telephone equipment and certain special use equipment such as a centrally located answering and recording equipment. The equipment may be located in a telephone central office or alternately in a separate location remote to both the customer&#39;s equipment and the telephone central office. When the equipment is in operation, the customer&#39;s phone is isolated from the telephone central office. If the customer goes &#34;off-hook&#34; the equipment is dropped and the customer&#39;s line is automatically connected to the incoming call.

This application is a continuation-in-part of my application Ser. No.589,151 filed on June 20, 1975 (now abandoned) and of co-pendingcontinuation-in-part application Ser. No. 872,850 filed on Jan. 27, 1978(now abandoned).

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to telephone answering systems and moreparticularly to systems employing call answering and recording equipmentlocated remotely from the telephone subscriber's equipment.

(2) Description of the Prior Art

Equipment has frequently been provided in prior art telephone systemsfor automatically answering calls to customer stations when the calledparty is not available to do so. Such equipment is usually arranged toanswer each call with a recorded announcement, to record any messagefrom the caller and afterward to play back the recorded messages to thecalled customer. A variety of other features are also usually suppliedby this equipment. For example, the customer generally is permitted torecord and check his own answer announcement, and to repeat and skipcertain passages during the playback period.

To provide these and other features present day equipment is usuallylocated on the customer's premises. As a result installation andmaintenance procedures are complicated because telephone companypersonnel must visit many locations to install and service equipment. Inaddition the customer desiring such answering service is presented withspace problems in locating the additional equipment adjacent to atelephone. Obviously such conditions increase the cost of service. Ithas been suggested that in order to reduce the service cost and simplifyinstallation and maintenance procedures, that the answering equipment belocated at a telephone central office. While such arrangements overcometo some extent the foregoing objections, the provision of many featuresof answering service which are frequently requested by customers is notpossible. For instance, the customer is unable to record his ownanswering announcement, instead he is required to use one prepared bythe telephone company and he is given no control over the repeating orskipping of messages during playback. The service is further restrictedwhen the customer can only obtain messages or playback at his ownstation.

Many of these objections have been overcome by a telephone answeringsystem disclosed in U.S. Pat. No. 3,141,931 to Alfred Zarouni. Howeverthe Zarouni patent teaches that each customer who desires telephoneanswering service be assigned two line appearances in the switchingnetwork at the telephone central office. One of these lines is connectedto the customer's answering equipment and with the line connected to thecustomer's station, it is used for ordinary telephone service. The otherappearance is connected to the answering equipment by means of an answerand record line. This latter line is a so-called "unlisted" line, thatis without a published directory number, and is used for allowing thecustomer to control his answering equipment.

It is obvious of course from the foregoing that the requirement for twotelephone lines and the attendant disadvantages thereto are less thandesirable. Such disadvantages include cost, service maintenance etc. aswell as the possibility that if a person other than the customersubscribing to such service, discovers the unlisted number, he may beable to playback and monitor messages not intended for him. The systemtaught by Zarouni obviously lacks the privacy retaining features ofprior art answering systems which were located on the customer's ownpremises.

Accordingly it is the principal object of the present invention toovercome the disadvantages of prior art telephone answering andrecording systems and particularly to provide a telephone answering andrecording system that may be located in a telephone central office orother centralized location which requires but a single telephone linebetween the customer's equipment and the centralized location for normaloperation and accordingly provides the same privacy associated with suchequipment when it is located at a customer controlled location.

SUMMARY OF THE INVENTION

The interface system of the present invention is utilized in connectionwith certain special use equipment such as telephone answering andrecording equipment and provides isolation between a telephonesubscriber's station or subset and a telephone switching system orcentral office. Specifically, when an incoming call from the switchingsystem to the answering and recording equipment is in process, thecustomer's subscriber's subset is disconnected from the switching systemand when the customer is communicating with the answering and recordingequipment, the switching system is isolated from the subscriber'stelephone.

The present interface system is designed for location at the samelocation as the telephone switching system while the associatedanswering and recording and other special equipment may be located atthe same location or alternately at a different location which would belimited only by the transmission capabilities of the lines connectingthe locations.

The interface system of the present invention includes relays whichprovide DC isolation of the switching system from the subscriber'ssubset and of the subscriber's subset from the switching system. It alsoincludes battery feed means for applying talking battery to thesubscriber subset during those times when a subset is isolated from theswitching system such as while a subscriber is communicating with theassociated answering and recording or other special equipment. A decoderis included which detects and translates touch calling multi-frequency(TCMF) signals received from the subscriber subset for control purposes.Program seize circuitry is connected to the decoder which controls therelays noted above to DC isolate the switching system from the subsetand connect by means of the included battery feed relay, talkingbattery, to the subset.

DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 taken in combination and arranged as shown in FIG. 18,constitute a composite block and schematic circuit diagram of telephoneanswering recording equipment in accordance with the present invention.

FIGS. 3 through 17 and 19 through 21 are schematic circuit diagrams ofvarious portions of the present invention shown in block form in FIGS. 1and 2 referred to above.

FIG. 3 is a schematic diagram of a record/play amplifier circuit inaccordance with the present invention.

FIG. 4 is a schematic diagram of an announcement motor circuit inaccordance with the present invention.

FIG. 5 is a schematic diagram of a remote circuit in accordance with thepresent invention.

FIG. 6 is a schematic diagram of a C-lead monitor circuit in accordancewith the present invention.

FIG. 7 is a schematic diagram of a ring count connect circuit inaccordance with the present invention.

FIG. 8 is a schematic diagram of a dictate circuit in accordance withthe present invention.

FIG. 9 is a schematic diagram of a tone decoder circuit in accordancewith the present invention.

FIG. 10 is a schematic diagram of an alarm circuit in accordance withthe present invention.

FIG. 11 is a schematic diagram of a time out timer circuit in accordancewith the present invention.

FIG. 12 is a schematic diagram of a message waiting tone circuit inaccordance with the present invention.

FIG. 13 is a schematic diagram of a standby tape circuit in accordancewith the present invention.

FIG. 14 is a schematic diagram of an announcement motor line seizecircuit in accordance with the present invention.

FIG. 15 is a schematic diagram of a program seize circuit in accordancewith the present invention.

FIG. 16 is a schematic diagram of a position/play circuit in accordancewith the present invention.

FIG. 17 is a schematic diagram of a tone oscillator circuit inaccordance with the present invention.

FIG. 18 shows the manner in which FIGS. 1 and 2 are to be arranged.

FIG. 19 is a schematic diagram of a midcycle shift circuit in accordancewith the present invention.

FIG. 20 is a schematic diagram of a beginning of tape circuit inaccordance with the present invention.

FIG. 21 is a schematic diagram of a tape counter circuit in accordancewith the present invention.

In FIGS. 1 and 2 single digit numbers are shown within the blocks whichindicate the terminal numbers shown in the associated detailed circuitdrawing figures. In this way the connection of the detailed circuitry tothe circuitry shown in the block diagram consisting of FIGS. 1 and 2 maybe more easily followed.

In each of the figures of the above described drawings the first digitof each three number indicia and the first two digits of each fournumber indicia indicates the drawing figure numbers where the componentreferenced by the indicia is located (transistor 412 appears in FIG. 4,transistor 1120 appears in FIG. 11, etc.), except in the case of certainrelays wherein the coil is located in the figure indicated by theindicia while its associated contacts may occur on a detached contactbasis (in a manner common to the telecommunication technology)throughout the other figures. Each relay contact combination carries thesame indicia as its associated relay coil, plus the addition of anexclusive identifying letter. For example, relay 1410 whose coil isshown in FIG. 14 has associated contacts 1410A which appear in FIG. 1and 1410B which appear in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the accompanying drawings and particularly FIGS. 1 and2 an incoming call to a subscriber served by the centralized answeringand recording equipment of the present invention will be described. Itshould be noted as mentioned previously that the bulk of the equipmentto be described may be located in the telephone central office butalternately may be located in some other central location. However it isrequired that for each subscriber being served with equipment inaccordance with the present invention, certain equipment for purposes ofproviding the necessary isolation of the telephone line during certainmodes of operation must be located at the telephone central office. Thisequipment which is categorically referred to as the line isolationequipment, consists of subset monitor relay 110, switching systemisolation relay 130, and subset isolation relay 140 and their associatedcontacts. Also included are capacitors 161, 162, 164, and diode 183. SeeFIG. 1.

Incoming ringing signals from the telephone central office serving thesubscriber are conducted from the subscriber's connector, at the IDF,over terminals T and R to terminals + and - appearing on the MDF wherethey are connected directly to the subscriber's telephone at hisresidence or place of business. This same ringing signal also appears atthe automatic answering and recording equipment located also in thetelephone central office or other convenient nearby location. Appearingon terminals T and R of the answering and recording equipment theincoming ringing signal is applied to the ring signal detector, shown asring count connector 700 (FIG. 7) and therein to the input of a bridgerectifier GR710. The output signal from the rectifier is applied to theinput of an optical-isolator 720 whose output is utilized to drive afilter section consisting of resistor 773 and capacitor 762. The outputis also applied to a differential amplifier 730. This amplifier acts asa comparator comparing the output signal from the optical-isolator to areferenced potential. If the output from the optical-isolator exceedsthat of the reference an output will be derived from amplifier 730. Itshould also be noted that the filter section connected to the output ofthe optical-isolator provides protection against dial transients. Theoutput of the amplifier 730 feeds a Schmitt trigger circuit 731 whichacts to shape the outgoing pulse for application to the input of a shiftregister counter 750. The output of the amplifier 730 is also applied toreset timer 740, which has a timing period of 10 seconds. The output ofthis timer is applied to the enable input of the shift register counter.In response to each incoming ringing burst the timer is reset so thememory is not cleared. If the call is abandoned after 10 seconds thetimer will clear the shift register. Assuming the call is not abandonedincoming pulses from the Schmitt trigger are applied to the clock inputof the shift register and counting begins.

The shift register 750 has a number of outputs each of which go true inresponse to a particular count. Depending upon the desired number ofrings before the recording and answering equipment operates, theappropriate output will be strapped to other circuitry. In theembodiment shown the output of the shift register that is strapped isthat associated with the receipt of a fifth incoming ring. After fiverings are received an output appears and is transmitted to theannouncement motor drive circuit 400 (FIG. 4) and particularly totransistor 411. Operation of transistor 411 is effective to start theannouncement motor 106. The tape used for announcements in the presentequipment incorporates at its beginning a foil section which conductsground through switch 1420 (FIG. 14). As the tape advances and ground isremoved from switch 1420, transistor 1401 operates relay 1410. It shouldbe noted at this time that while a metalized portion of the tape is usedand an electrical contact performs removal of ground, to effectactuation of the transistor, it may also be possible to use an opticalor light reflecting arrangement or some form of pressure sensitivemicroswitch at this point, it only being required that as the tapeadvances a signal is forwarded which will alternately operate andrestore relay 1410.

In response to the operation of relay 1410 through its contacts 1410Athe telephone line is now connected to the ringing signal monitor Triac199. Relay 1410 also at its contacts 1410C, breaks the connection toground over which capacitor 262 was previously energized, and connectsone side of capacitor 262 through resistor 275, break contact 240E andmake contact 1410C to relay 250. Capacitor 262 in response to itsdisconnection from ground starts to discharge towards relay 250operating it. In response to operation of relay 250, at contacts 250A,voltage is applied to the gate of Triac 199 and Triac 199 becomesconductive, connecting the telephone line directly to the calling partycontrol relay 150. In this manner the telephone line is bridged andringing from the telephone central office is stopped by virtue of thecompletion of the loop formed by relay 150. After a short period of timecapacitor 262 completely discharges causing relay 250 to be restored.

Operation of relay 150 at contacts 150A, connects ground throughresistor 174 to subset isolation relay 140 causing relay 140 to operateat this time. Relay 140 in operating isolates the subscriber's telephoneline as far as DC signals are concerned from the telephone line byoperation of break contacts 140A and 140B. Relay 140 at its associatedmake contacts 140A and 140B connects subset monitor relay 110 directlyto the subscriber's line to monitor the subscriber's telephone line foroff-hook conditions at the subscriber's telephone instrument.

The incoming call as noted previously after five rings has now beenconnected to the centralized answering and recording equipment. Theequipment is now prepared to playback to the accessing telephonesubscriber the announcement message. Audio signals from the announcementtape are picked up by head 105, coupled through break relay contacts810D and 1610A, to the input of the record/playback amplifier 300wherein signals are amplified and then applied through a 15 ohm resistor176 to the line transformer 109. The return path for this signal is toground. This signal is then coupled to the opposite windings oftransformer 109 which are connected across the coil of relay 150 andalso across the telephone line. In this manner the message on theannouncement tape advising the subscriber that he has accessed ananswering device, is coupled over the telephone line to the accessingtelephone subscriber.

After the announcement has been completed a tone at the end of themessage recorded on the same tape is played to initiate what is referredto hereinafter as mid-cycle shift. This tone picked up by thetransformer 109 is coupled to the input of the differential toneamplifier 910 included in tone decoder 900 (FIG. 9). Tone decoder 900and program seize circuit 1500 comprise the calling signal detectioncircuitry.

The tone decoder circuitry shown in FIG. 9 will now be described indetail. Incoming signals are coupled to integrated circuits (IC) 920 and930 which are commercially available tone detector units. In response toreceipt of any of four frequencies, 1209 Hz, 697 Hz, 1477 Hz, and 941Hz, a digital "low" signal appears on the output terminal of either ofthe integrated circuits depending upon which signal has been received.In the case of 1209 Hz it appears on the output of IC920, in the case of697 Hz, it appears on the output of the same IC while 1477 Hz appears onthe output of IC930, and 941 Hz also appears on the output of that sameIC. These outputs are then coupled through logic gate circuitry 940 totimer stages that are a portion of IC950. The timer puts out an outputsignal in response to a combination of 1209 Hz and 941 Hz, in responseto the combination of tones of 1477 Hz and 697 Hz, and in response toreceipt of the combination of 941 Hz and 1477 Hz signals. Hereinafterthe first combination of 1209 Hz, and 941 Hz will be referred to asthe * frequency, the combination of 1477 Hz and 697 Hz will be referredto as "3", and the 941 Hz and 1477 Hz will be referred to as #. Theseoutputs are then applied (through inverter stage 960) from the tonedecoder circuitry to the remaining circuitry of the centralizedanswering and recording equipment, as required.

Returning again to the discussion of midcycle shift: Signal tone isreceived initially at the tone decoder 900 previously described andbecause it actually consists of a combination of 941 Hz and 1477 Hztones an output appears on the # output of tone decoder. This outputsignal is then applied to the gate of SCR1901 (FIG. 19) causing it toconduct. In response to conduction of SCR1901 relay 240 operates. Itshould be noted that the operating path for relay 240 was throughcontacts 150B of relay 150 and also contacts 520C of relay 520 toground; and from battery through break relay contacts 120A and 520E.Operation of relay 240 at contacts 240A establishes a short circuitaround contacts 1410A of relay 1410 to hold the line for the incomingmessage cycle. Operation of relay 240 is also effective at contacts240F, to operate integrated circuit 1110 to start timing. IC1110 is acommercially available "Norton" type amplifier operated to function as atimer. IC1110 is a part of the time-out timer 1100 (FIG. 11) and isadjustable over a range of 30 to 60 seconds by resistor 1131. Relay 240also applies ground at make contacts 240B through resistor 172 to theincoming erase head 101 and ground through diode 182 to the switch inputof the record play amplifier 300 (FIG. 3), causing the amplifier toswitch from the playback mode to the record mode.

Incoming signals received over the telephone line at transformer 109 arenow coupled from the transformer to the record input of therecord/playback amplifier 300. Signals amplified therein are taken fromthe record output and applied through break contacts 810C and contacts1610B to the incoming record head 104 wherein they are coupled tomagnetic recording tape, used as the recording medium in the presentequipment.

While it has been shown in the present equipment to use recording tapeand conventional pick up and record heads in the conventional taperecording/playback arrangement, it should also be understood that otherforms of memory might also be utilized and incoming information might beapplied thereto in digital form and likewise recovered in the samemanner.

The incoming message is now recorded. Termination of the incomingmessage or the announcement message may be made at any time during thepreviously mentioned description in the following manner: First the 30second timer IC1110 operates after its time period of 30 seconds tooperate relay 230. In response to operation of relay 230, SCR1901 ofmid-cycle shift circuit 1900 (FIG. 19) is rendered nonconductive,releasing relay 240. Relay 240 restores after a short period of time(approximately 3 seconds) because of the discharge time of capacitor262. All other previously operated relays also release restoring theunit to its normal or unoperated condition.

A second manner of disconnecting the answering equipment occurs when thecalling party hangs up. At this time in a telephone central officehaving calling party release, the loop voltage goes momentarily to zeroand SCR199 becomes nonconductive causing relay 150 to release which inturn at make contact 150B causes relay 240 to release in a mannersimilar to that previously outlined which in turn will cause the otherrelays to also restore. The third manner in which the equipment may bedisconnected occurs when the subscriber having answering serviceprovided by the machine of the present invention answers a call whilethe machine has already seized the telephone line. At that time when thesubscriber goes off-hook he completes a loop over terminals - and + atthe MDF input to relay subset monitor 110. At this time relay 110operates because of the completed loop. The associated terminals ofrelay 110 connects at terminal 110A, battery to switching systemisolation relay 130, causing it to operate through diode 183 whichconnects to ground on the C lead extending from the telephone centraloffice at terminal C to the IDF. Operation of relay 130 is effective atits associated contacts 130A and 130B to open the telephone line fromthe telephone answering machine causing the conditions to be interpretedthe same as when the calling party disconnects as outlined previously.

Message Recovery or Playback By the Telephone Subscriber

When the subscriber having answering service provided by the presentequipment goes off-hook he receives dial tone via the leads from the IDFterminals T and R at the telephone central office and extending out fromthe + and - terminals at the MDF. The telephone central office alsoconnects ground to the C lead of the IDF at this time. Although groundthrough diode 183 is present, relay 130 is not operated. This ground isalso connected at terminal 2 to the C lead monitor circuitry 600 (FIG.6) and particularly to resistor 672 and to the input of anoptical-isolator 610. The return path from the optical-isolator is tothe coil of relay 140 which is not operated at this time. Neither relay130 or 140 operate, since insufficient current flow is available tocause them to operate because of the presence of resistor 672 which hasa resistance of 100,000 ohms. Current flowing through theoptical-isolator causes an output which is extended to one of the inputsof comparator amplifier 620. If the voltage appearing on the input is ofsufficient magnitude compared to the reference voltage connected to theother input of amplifier 620, an output appears from comparatoramplifier 620 and is applied to one of the inputs of an associatedamplifier 630 serving as an AND gate whose output is connected totransistor 682. The output from the comparator amplifier is alsoconnected to a timer section 640 of the "C LEAD" monitor 600 whoseoutput provides the other input of the AND gate.

The output from the timer is combined with the direct output from thecomparator amplifier in the AND gate circuitry to cause operation oftransistor 682. After a predetermined period of time the timer times outand through the previously outlined circuitry transistor 682 is turnedoff. The duration of operation of the transistor is approximately 5seconds. During the operation of transistor 682, relay 210 is operatedand through its contacts 210A capacitively couples transformer 109 tothe telephone line.

If previously recorded messages which have not been retrieved arepresent on the recorded message tape of the answering unit, SCR1212 ofmessage waiting circuit 1200 (FIG. 12), will be in the conductive mode.This occurs because it was gated on during the incoming recording ofprevious messages. It is gated on by relay 240 and will remain on untilthe operation of relay 1620 which will be described hereinafter. SCR1212will conduct ground through relay contacts 210D and diode 1211 to relay230, causing relay 230 to operate at this time. Operation of relay 230causes the tone oscillator 1700 (FIG. 17) which includes transistor 1710and associated components to turn on at this time. This oscillatorproduces a tone (approximately 1400 Hz) which appears on the collectorof transistor 1710 and then is coupled through resistor 1731 and relaycontacts 210B to the play input of the record/playback amplifier 300.Amplified signals at the playback output are then coupled to thetelephone line through transformer 109 in the manner previouslydescribed. At the subscriber's instrument a message waiting tone (1400Hz) is heard to indicate the presence of messages on the tape (at thecentralized answering and recording equipment).

After five seconds this tone will disappear in the manner previouslydescribed. During this same period of time signals from the telephoneline are also coupled to the tone decoder 900 (FIG. 9) in a mannerpreviously described in connection with midcycle shift. The # tone isdetected and SCR1520 will be caused to conduct and to operate relay 1510over a path that extends through relay contacts 210C. Operation ofprogram seize circuit 1500 (FIG. 15) which with tone decoder 900comprise the calling signal detection circuitry, commences when relay1510 at its contacts 1510B places a short across the leads to relays 130and 140 which will cause relay 130 to operate. The operating path forrelay 130 is from the grounded C-lead via diode 183 and from batterythrough relay coil 140 and contacts 1510B. Because of itsslow-to-operate characteristics relay 140 does not operate at once.Operation of relay 130 contacts 130D will then prevent relay 140 fromoperating at this time. Also at associated break contacts 130A and 130Bisolation of the central office at the line IDF from the subscriber orthe answering machine will also take place. The telephone line is nowcapacitively coupled at the IDF by capacitor 161 and 162 for monitoringof incoming ringing signals.

DC power is now fed to the subscriber through battery feed relay 120 andrelay contacts 1510A and 1510F to the telephone line. The loopresistance of the subscriber's telephone line will now hold relay 120operated, which in turn will hold relay 1510 operated at contacts 120A.At this point relay 210 will release as the C-lead monitor circuit 600is no longer conductive.

The unit has now been seized and the subscriber will hear a standbytone. This tone originates with battery through contacts 120A, throughresistor 272 and diode 286 to standby tape circuit 1300 (FIG. 13) andthrough resistor 1340 and diode 1330 to transistor 1310 to causetransistor 1310 to conduct at this time. Conduction of transistor 1310will cause operation of relay 230. When relay 230 operates the toneoscillator 1700 (FIG. 17) which includes transistor 1710 turns on andtone at the collector through resistor 1731 through relay contacts 210Band through resistor 196 is applied to the input of the playbackamplifier 300. The output from the playback amplifier is connected tothe telephone line in the manner previously described.

On hearing standby tone, the subscriber (assuming that the subscriberhas a touch calling telephone) will push the digit "3" pushbutton togenerate the appropriate signals associated with this number which willbe conducted over the intervening telephone line and through contacts1510C and capacitor 166 to a winding on transformer 109. Return is fromthe transformer back to the telephone line. The tone signals will becoupled from the opposite winding of the transformer 109 to the input ofthe tone decoder 900 (FIG. 9). Input comes in on terminal 1 of the tonedecoder 900 and the output appears on terminal 5. The output on terminal5 is then applied to position/play circuit 1600 (FIG. 16) at the gate ofSCR1630 to render it conductive. The output from the tone decoder isalso applied to the base of transistor 1640 to render it conductive toplace a short across relay 1610 to inhibit its operation at this time.After release of the tone, transistor 1640 becomes nonconductive andrelay 1610 operates through the previously established operating pathset up through SCR1630 and through diode 1692, resistor 1684 and throughcontacts 120A to battery. Operation of relay 1610 of position/playcircuit 1600 (FIG. 2) establishes a path through relay contacts 1610Cand 1510E to initiate operation of the incoming motor designated 107.Ground from SCR1630 causes standby tape circuit 1300 (FIG. 13)transistor 1310 to become nonconductive thus releasing relay 230 and thetone oscillator 1700 at this time.

The tape on which incoming recorded messages have been recorded alsoincludes a separate track on which indicia indicate the amount of tapein time that has been used. These markings may be in minutes, seconds,or any other appropriate form. Signals as to the amount of tape that hasbeen used are thus in this manner picked up and coupled to the head 103and through the playback amplifier 300 through contacts 1610A and 1620Aof relay 1610 and relay 1620 respectively. After amplification by theplayback amplifier they are connected to the telephone line through thetransformer 109 in the manner previously described. These signals arethen heard by the subscriber and indicate the approximate amount of timewhich has been devoted to recording on the remotely located recordingequipment at the telephone central office.

The subscriber may hang up now which will cause the machine todisconnect in the manner to be described hereinafter. Or alternately hemay retrieve the messages that have been recorded at this time.

Assuming now that the subscriber desires to retrieve the previouslyrecorded messages, the subscriber will operate the "3" pushbutton on histouch calling telephone, transmitting the associated combination of twotones to the answering and recording equipment wherein they will bedetected in the manner previously described. This detection results inan output from the number 5 terminal of the tone decoder which willcause position/play circuit 1600 (FIG. 16) transistor 1640 to conductplacing a shunt around associated relay 1610, causing relay 1610 torestore. Prior to its restoration relay 1610 kept capacitor 1672charged. Upon its release capacitor 1672 discharges through a path viaresistor 1689 to the base of transistor 1660 which in turn will causerelay 1620 to operate. Relay 1620 operates and locks over its associatedcontacts 1620D and diode 1693 to ground and via resistor 1687 tobattery. The operation of relay 1620 at contact 1620A switches the inputof the playback amplifier from the position heat 103 to the incomingpick up head 104. At this time relay 1610 is restored and relay 1620 isoperated. This operation will cause the tape to rewind by placing groundthrough relay contacts 1610C and relay contacts 1620B to the headposition motor 108, causing it to remove the head structure from contactwith the associated tape and engage the rewind idler mechanism. As longas the tone is maintained by the subscriber the tape will be rewound.While the tape is moving a switch 1430 known as the tape motion switchin the announce motor seize circuit 1400 (FIG. 14) is held in alternateoperated and restored positions. Pulses from this switch are applied tothe input of Schmitt trigger circuit IC2111 in tape counter 2100 (FIG.21). The output of the Schmitt trigger provides an input to integratedcircuit IC2120 which in combination with integrated circuits IC2130 andIC2140 (each of which is a commercially available four-bit binary ripplecounter) comprise a so called "up-down" 12 bit counter. This unit mayutilize any of the many conventional forms prevalent in the prior art.

Prior to the operation of relay 1620 the counter 2120 was held in thereset mode by application of ground through contacts 1620C. When relay1620 removes ground at those contacts, the counter becomes enabled byremoval of the ground. The same ground was also available to holdcomparator IC2020 of the begin tape circuit 2000 (FIG. 20) in the resetcondition. That ground which caused the head position motor 108 toretract the head from contact with the tape in the rewind mode, is alsoavailable from contacts 1610C to reset the timer section of IC2112through diode 2171. The output of the timer section from 2112 is appliedto the "up-down" control of the counter 2120. When the timer is in thereset condition the counter counts "down" while in the time-outcondition it counts "up". Since the unit is in the rewind mode, countingis down from zero position.

At the same time switch 1430 of announcement motor line seize circuit1400 (FIG. 14), is pulsing the Schmidt trigger IC2111, it is alsoapplying ground pulses through a pulse shaping network consisting ofdiode 1404, resistor 1423, diode 1405, resistors 1424 and 1425,capacitor 1431, and resistor 1426. Its output is applied to thebeginning of tape circuit 2000 (FIG. 20) comparator section of IC2020.The output of the comparator section of the IC2020 controls a timersection IC2030 through diode 2063. As long as pulses from the switch1430 are present pulses are applied to the input of the comparatorcircuit which will maintain the associated timer in the reset condition.Upon the pulses from the switch stopping, the timer portion of IC2030will time-out causing relay 2010 to operate. Relay contacts 2010A willplace a short circuit across the T and R leads of the telephone lineremoving battery from the subscriber's telephone and causing the tone tostop, for both the machine and the customer. Because tone is no longerpresent the tone decoder will release the hold which is present in theform of a signal at the base of transistor 1640, to cause relay 1610 toreoperate. With both relays 1610 and 1620 operated a ground will bepresent for motor 108 to drive the head assembly back to engage the tapeas this time. This action places the machine in the playback mode.Because the unit is in the playback mode IC2120 is in a count "up" mode.

Messages recorded on the tape are thus picked up by pick up head 104,amplified by the playback amplifier 300 and applied over linetransformer 109 to the telephone line where they are conveyed over thetelephone line to the subscriber's instrument where they are monitored.When the machine goes into the playback mode pulses from the tapeapplied through switch 1430 are again available. They reset the timer2030 that is a portion of beginning of tape circuit 2000 to cause relay2010 to release and open the short circuit applied across the telephoneline.

At any point during the monitor or playback mode the subscriber mayoperate the number "3" button of the touch calling telephone which willcause the associated machine to go into the rewind mode.

If the subscriber desires to stop monitoring, several courses of actionare available. First he may simply hang up to cause the unit to go intothe fast forward mode which will be described hereinafter. Alternatelythe unit may be allowed to go until the counter returns the unit tostandby at which time standby tone through relay 230 will be applied tothe telephone line to indicate that the playback mode is completed.Another alternative permits the subscriber to push the # button on hisassociated touch calling telephone unit, which will cause the unit to goin the standby mode instantly. For better understanding of the abovementioned modes of termination of the playback operation, they will bedescribed in more detail hereinafter.

First assuming the subscriber wishes to terminate playback by operatingthe # button at his touch calling telephone. Tone is decoded in themanner previously outlined by the tone decoder circuitry and appears atthe number "7" terminal of the tone decoder as an output signal. Thissignal is then applied through diode 293 to the position/play circuit1600 (FIG. 16) and resistor 1685, to the base of transistor 1650,causing transistor 1650 to conduct, placing a shunt across relay 1620causing it to restore. This in turn causes relay 1610 to restore placingthe unit in the standby mode. If the subscriber allows the playbackoperation to go on to its ultimate end, tone is returned indicating theunit is in the standby mode and the counter will cause the unit toreturn to standby. This occurs when the counter gets to the zeroposition at which time the comparator circuit 2113 recognizes an outputfrom the counter and applies an output signal through diode 2177 andthrough resistor 1685 to the base of transistor 1650. When this happenstransistor 1650 is operated placing a shunt across relay 1620 causing itto restore, which in turn will cause relay 1610 to restore in the mannerdescribed above. When the subscriber elects to merely hang up at thesubscriber station, the DC loop to relay 120 is broken and relay 120will restore. This in turn causes relay 1510 of program seize circuit1500 (FIG. 15) to restore. When relay 1510 restores relay 130 willrestore and if the unit is in the standby condition all other relayswill restore at this time. If the unit is in the playback mode at thistime relay 1620 will hold relay 1610 and itself operated over a paththrough its own contacts 1620E to battery. This places the unit into thefast forward mode by applying a ground through relay contacts 1610C andrelay contacts 1510E to the fast forward circuitry. This applies groundto the head position motor 108, causing the heads to be retracted orremoved from contact with the tape. This also causes relay 220 tooperate. Combination of operation of the relay 220 and movement of motor108 is effective to place the associated linkage mechanism in the fastforward mode. It should be noted that contacts on relay 220 insure thatthe heads are in contact with the tape, before the mechanism is switchedto the fast forward mode. This arrangement eliminates mechanicaldifficulties. Once the unit has been placed into the fast forward mode,relays 1610 and 1620 will restore from the counter circuit as previouslydescribed. Ground from the fast forward circuitry also prohibits theunit from decoding any incoming tones received over the telephone lineunitl the unit has reset.

When an end of tape condition exists which will result in switch 1430 nolonger producing output pulses, relay 2010 will operate in a mannerpreviously outlined to cause relay 120 to also operate. This will causeall operated relays to restore. Once the equipment has reached the endof tape condition described previously the equipment will no longeranswer any incoming messages until such time as the subscriber hasaccessed the equipment and reset it.

As noted previously when the answering euipment of the present systemhas been accessed by a party attempting to contact the subscriberassociated with the equipment and has been unable to do so he may leavea recording. As a preliminary to making that recording he receives fromthe centralized automatic answering and recording equipment a message.This answering message may be prerecorded, or alternately, be recordedby the subscriber having answering and recording service in thefollowing manner:

The subscriber will seize the unit by operating his touch callingtelephone # key to place the unit in the standby mode in the mannerpreviously outlined. As soon as the unit has gone into the standby modethe subscriber will push the * button on the touch calling telephone tocause an output at terminal 6 of the tone decoder 900 (FIG. 9). Thisoutput signal will be applied through resistor 842 of dictate circuit800 (FIG. 8) to turn on SCR821. This signal also goes through diode 823to turn on transistor 822. Transistor 822 provides a shunt path forrelay 810. When tone is removed by the customer, relay 810 which hasbeen conditioned will now operate over the holding path through SCR821which was turned on previously. The remaining operating path is throughresistor 844 back through the relay contacts 120A.

When relay 810 operates ground is applied through contacts 810B of relay810 to the record switch input of the record/playback amplifier causingit to go into the record mode. Ground is also applied through resistor171 to the announcement erase head 102. High frequency bias signals, andaudio signals, through relay contacts 810C and 810D are applied to therecord head 105, by the record oscillator mechanism to provide forrecording of a new message. Old messages are erased by a DC voltagewhich is applied to the erase head. Operation of relay 810 also appliesthis signal at the base of transistor 411 of announcement motor circuit400 (FIG. 4), causes it to operate which will cause the announcementmotor 106 to operate. Ground is extended through contacts 810F andresistor 431 to charge capacitor 421. As noted previously when thecontacting foil moves forward with the tape, switch 1420 of announcementline seize circuit 1400 (FIG. 14) operates causing transistor 1401 tooperate which will cause relay 1410 to operate. When relay 1410 operatesSCR821 will be the rendered nonconductive, however relay 810 will remainoperated through contacts 810E on relay 810 and contacts 1410F on relay1410. Using the handset of the telephone the customer will now recordany message he desires.

After he has completed the message he operates the # signal to recordthe # tone which is used for mid-cycle shift in the answer/recordarrangement or alternately he operates no button. When no tone isrecorded the machine will not go into a mid-cycle shift. Thisarrangement is used in the answer only mode.

When the contact foil on the tape which is of the endless loop typeagain appears at the switch 1420, transistor 1401 is renderednonconductive which will cause relay 1410 to restore. This in turn willat contacts 1410F cause relay 810 to restore. Motor 106 however willcontinue running with the discharge of capacitor 421 through resistor431 to the base of transistor 412. In this manner the contact foil willagain move past switch 1420 and cause relay 1410 to operate. The unit isnow in the check function mode. During the check mode the just recordedannouncement will be played back over the telephone line to thesubscriber so he may verify that the announcement has been madecorrectly. As the machine drive motor 106 continues to advance theanswer tape is moved forward and audio signals that have been recordedare picked up by pick up head 105, conducted to the input of the playamplifier 300, taken from the outputs thereof and applied to transformer109 and back over the telephone line to the subscriber. The subscriberhaving verified the message has been correctly recorded simply hangs upand disconnects, wherein the machine will disconnect in the mannerpreviously described.

If it is desired the subject unit may be equipped with a voice controlcircuit (1800) which is associated with the time-out timer 1100 whichkeeps resetting the time-out timer as long as voice signals are presentin the telephone line. The voice control circuitry of itself isconventional.

If the announcement contactor is for some reason inoperative, pulses areno longer available through diode 1023 of alarm circuit 1000 (FIG. 10)to keep the timer IC1020 reset. Comparator 1020 will operate and apply asignal to transistor 1022 which in turn will operate an alarm lamp 1021on the unit and operate relay 1010. Relay 1010 will then extend thisalarm condition to the telephone central office where it may be utilizedin any practical manner. This alarm unit likewise could be used tomonitor other functions of the unit.

It should be noted that if a subscriber using the machine is in theprocess of making an announcement or reviewing recorded messages and anincoming call is received from the telephone central office, a ringingsignal through capacitors 161 and 162 will be heard at the subscriber'sinstrument and accordingly by simply hanging up the handset at theinstrument, release will occur in the manner previously describedcausing relay 120 to restore and consequently allow the call from thetelephone central office to be conducted over the MDF terminals to thesubscriber line. In this manner emergency calls may be received as wellas permitting the subscriber not to miss any calls during the playbackor recall mode of operation.

While but a single embodiment of the present invention has been shown,it will be obvious to those skilled in the art that numerousmodifications may be made without departing from the spirit and scope ofthe invention. It will be particularly obvious that only certainstandard tone combinations have been employed for control of thecircuitry of the present invention. In view of this it would be mostobvious that additional features can be included within the tonedecoding capability of the present equipment. Such additional featuresmay include the provision of circuitry for turning the equipment "on" or"off" from the subscriber's instrument or remotely, or providing a fastforward mode of operation for the tape equipment.

What is claimed is:
 1. An interface system, connected to a telephoneswitching system and to a subscriber subset equipped with calling signalgenerating means, said interface system including: switching systemisolation means; battery feed means connectible to said subset; callingsignal detection means including signal decoding means connected to saidsubset, initially operated in response to a calling signal generated atsaid subset, and program seize means connected to said decoding means,operated in response to said decoding means, to operate said switchingsystem isolation means to DC isolate said switching system from saidsubset and connect said battery feed means to said subset; and saidbattery feed means operated in response to connection to said subset tomaintain said program seize means operated after termination of saidcalling signal.
 2. An interface system as claimed in claim 1 wherein:said switching system isolation means comprise a relay including a coiland a plurality of switching contacts; said coil energized in responseto operation of said program seize means and a portion of said pluralityof contacts operated in response to said coil energization to DC isolatesaid switching system from said subset.
 3. An interface system asclaimed in claim 1 wherein: said battery feed means comprise a relayincluding a multi-winding coil connected to a source of direct currentpotential and connectible to said subset, and at least one switchingcontact operated to maintain said calling signal detection meansoperated.
 4. An interface system, connected to a telephone switchingsystem including ringing signal generating means, and to a subscribersubset, said interface system including: subset isolation means, subsetmonitor means connectible to said subset; conditioning means connectedto said telephone switching system, operated in response to a ringingsignal from said generating means; and ringing signal monitor meanscomprising a Triac connected to said switching system in response tooperation of said conditioning means, and a relay connectible to saidswitching system; said relay connected to said switching system inresponse to operation of said Triac on receipt of a ringing signal fromsaid switching system to terminate said ringing signal; said relayincluding a coil connectible to said switching system energized inresponse to said connection, and at least one switching contact operatedin response to energization of said coil to operate said subsetisolation means to DC isolate said subscriber subset from said switchingsystem and connect said subset monitor means to said subscriber subset.5. An interface system as claimed in claim 4 wherein there is furtherincluded: switching system isolation means; said subset monitor meansoperated in response to said subset initiating a call for service, tooperate said switching system isolation means to further DC isolate saidswitching system from said subscriber subset.
 6. An interface system asclaimed in claim 4 wherein: said subset isolation means comprise a relayincluding a coil and a plurlity of switching contacts; said relay coilenergized in response to said ringing signal monitor means and a portionof said switching contacts operated in response to energization of saidrelay coil to connect said subset to said subset monitor means.
 7. Aninterface system as claimed in claim 5 wherein: said subset monitormeans comprise a relay including a multi-winding coil connected to saidsubscriber subset and at least one switching contact operated inresponse to connection of said relay to operate said switching systemisolation means.
 8. An interface system as claimed in claim 5 wherein:said switching system isolation means comprise a relay including a coil,enegized in response to operation of said subset monitor means and aplurality of switching contacts operated in response to energization ofsaid coil to DC isolate said switching system from said subset.
 9. Aninterface system, connected to a telephone switching system includingringing signal generating means, and to a subscriber subset equippedwith calling signal generating means, said interface system including:switching system isolation means; subset isolation means; subset monitormeans connectible to said subset; battery feed means connectible to saidsubset; calling signal detection means including signal decoding meansconnected to said subset, initially operated in response to a callingsignal generated at said subset and program seize means connected tosaid decoding means, operated in response to said decoding means tooperate said switching system isolation means to DC isolate saidswitching system from said subset and connect said battery feed means tosaid subset; said battery feed means operated in response to connectionto said subset to maintain said program seize means operated aftertermination of said calling signal; conditioning means connected to saidtelephone switching system, operated in response to a ringing signalfrom said generating means; and ringing signal detection means connectedto said switching system in response to operation of said conditioningmeans, operated in response to ringing signals received from saidswitching system to operate said subset isolation means to DC isolatesaid subscriber subset from said switching system and connect saidsubset monitor means to said subscriber subset; said subset monitor tomeans operated in response to said subset initiating a call for service,to operate said switching system isolation means to DC isolate saidswitching system from said subset.